The optoelectronics industry has made a recent decision to reduce the size of the optical connectors previously used, e.g. the SC connector, to roughly half the size, with corresponding reductions in the size of the transceiver module which mate to the connector. Such a transceiver would mate to an optical connector carrying two fibers, one which carried the outgoing signals from the transmitter, and the other which carried the incoming signals to the receiver. The connectors and transceivers made in accordance with this decision are called “Small Form Factor” (SFF) components. The space allotted to the optoelectronic and supporting chips, circuits and electrical connections, along with the mating optoelectronic interconnection, is typically only about 13 mm×49.5 mm in the plane, and 9.8 mm high. This requirement puts stringent constraints on the design of the transceiver, particularly because the components packaged within this small space must meet the operating specifications while low fabrication costs are maintained.
Two major complicating factors in the development of transceivers are the facts that:                no one optical connector has been chosen as the SFF standard. Major contenders for such connectors include the LC, the MTRJ, the VF45, and the SCDC. For a discussion of the various connectors used with SFF (see J. M. Trewhella, “Performance Comparison of Small Form Factor Fiber Optic Connectors”, Proceedings of 49th ECTC, pp. 398–407, 1999) and        most of the optoelectronic chips (laser and receiver) used in the industry are hermetically sealed in TO cans. The use of these cans presents extra packaging challenges because they are large and awkward on the SFF scale, and are typically made with very wide tolerances.        
The fabrication of a transceiver which mates to the LC connector has been described previously (W. Hogan, “A Novel Low-Cost Small-Form-Factor Transceiver Module”, Proc. 50th ECTC, pp. 725–732, 2000). However, the packaging problem associated with the LC connector is simpler with than that of any other connector, primarily because of the LC's relatively wide fiber-to-fiber spacing (transmitter fiber to receiver fiber) in the connector, i.e. 6.25 mm, which permits the TO cans to be positioned side by side. No such solution is viable for the MTRJ connector, because that connector has a fiber—fiber spacing of only 750 micrometer, while the width of a TO46 can is about 5.4 mm. Clearly, an optical space transform must be made for the MTRJ connector in order to change the 750 micrometer lateral spacing into a spacing compatible with the use of TO cans.
In the past, several optoelectronic devices have been built with waveguides constructed by embedding standard optical fibers in the devices, as well as with non-fiber waveguides specially constructed on the device itself. Either technique for waveguide construction may be used for fabricating a transceiver which mates to an MTRJ connector. In particular, a silicon substrate positioned in the transceiver may be used as the carrier of an “optical coupler” (OC) which serves to interconnect the fibers in a cable terminated by an MTRJ connector to the optoelectronic chips (laser and photodetector). This optical coupler supports the waveguides which are used for the optical interconnect.
In particular, V-shaped grooves are precision-etched in silicon to carry two optical fibers using known silicon-optical bench (SiOB) techniques, one each for the transmitter and receiver functions, while larger grooves are simultaneously etched to carry the 750 micrometer diameter pins needed for interfacing to the MTRJ connector. The fibers are anchored to the Si carrier by means of epoxy; the ends of the assembly are then polished to provide the finish required by the fiber faces.
However, because of severe space limitations, the required space transform must be confined to a very short longitudinal distance, which consequently requires that the fibers be subjected to a very small bend radius. Small fiber bend radii are usually unacceptable, however, since extensive studies have shown fiber failure under conditions of small bend radius because of stress-induced cracking (see V. Annovazzi-Lodi et al, “Statistical Analysis of Fiber Failures under Bending-Stress Fatigue”, J. Lightwave Tech., vol. 15, pp. 288–293, 1997).
In view of the foregoing, a need has been recognized, inter alia, in connection with overcoming the shortcomings and disadvantages encountered in connection with the conventional arrangements discussed above.